An organic light emitting display panel refers to a panel comprising an organic light emitting device, for example an OLED (Organic Light Emitting Diode) or other organic electroluminescent (EL) elements. The most common light emitting device is an OLED. An organic light emitting display panel is a panel that utilizes an organic light emitting display device, wherein every pixel structure of the panel comprises one organic light emitting device. Because an organic light emitting device is a self-illuminating display device, so such a display panel does not require a backlight. An organic light emitting device is gradually becoming a shinny spot in the field of flat panel display and will play an important role because of its advantage of thinness, lightness, self-illuminating, broad view angle, high sharpness, high brightness, quick response, low energy consumption, broad operating temperature range, resistance to vibration and so on.
An OLED light emitting device is a light emitting device of current driving type which requires a large driving current during normal operation. The larger the driving current that is provided by a driving circuit for the OLED, normal work of the OLED is better guaranteed, allowing decrease in energy consumption of the OLED. A thin film transistor (TFT) driving an OLED to emit light is very important, and the higher mobility carriers in an active layer of the TFT have, the larger the driving current driving the OLED is.
Currently, the TFT in an OLED display panel mainly comprises an amorphous silicon TFT and a low temperature polysilicon TFT. The carriers in a low temperature polysilicon TFT have a mobility greater than that of the carriers in the amorphous silicon TFT by at least two orders. Therefore, most of TFTs in current OLED display panels are low temperature polysilicon TFTs.
The current conditions for making a low temperature polysilicon TFT are relatively harsh, and generally require deposition of amorphous silicon, performing a dehydrogening process afterwards, performing a laser annealing after the process and then exposing and etching, which needs at least 3-4 masking processes. The whole process is complicated and has a low yield. Moreover, a low temperature polysilicon TFT is prepared at a high temperature and is not appropriate to be prepared on a flexible substrate.